Leading-Order Determination of the Gluon Polarization from high-$p_T$ Hadron Electroproduction

TL;DR

This study measures the gluon polarization in the nucleon by analyzing high-$p_T$ charged hadron electroproduction, providing leading-order estimates consistent across different targets and kinematic conditions.

Contribution

It introduces a leading-order extraction method of gluon polarization from high-$p_T$ hadron data using the Pythia Monte Carlo generator, with results consistent across various conditions.

Findings

Gluon polarization $rac{ riangle g}{g}$ is approximately 0.049 at $ ext{x} ext{= } 0.22$

Results are consistent across different targets and kinematic domains

Uncertainties include statistical, experimental systematic, and model-dependent errors.

Abstract

Longitudinal double-spin asymmetries of charged hadrons with high transverse momentum $p_T$ have been measured in electroproduction using the \hermes\ detector at \hera. Processes involving gluons in the nucleon have been enhanced relative to others by selecting hadrons with $p_T$ typically above 1 GeV. In this kinematic domain the gluon polarization has been extracted in leading order making use of the model embedded in the Monte Carlo Generator \Pythia\ 6.2. The gluon polarization obtained from single inclusive hadrons in the $p_T$ range 1 GeV $< p_T <$ 2.5 GeV using a deuterium target is $\frac{\Delta g}{g}(\langle x\rangle, \langle \mu^2\rangle)=0.049\pm 0.034 (stat)\pm 0.010 (sys\textrm{-}exp)^{+0.126}_{-0.099}(sys\textrm{-}models)$ at a scale $\la\mu^2\ra=1.35~{\rm GeV}^2$ and $\langle x\rangle = 0.22$. For different final states and kinematic domains, consistent values of \DGG\ have been found within statistical uncertainties using hydrogen and deuterium targets.